Provide a detail explanation for every case:
1. There are 6 types of rolls available in a bakery, in quantities of dozens of each type. You want a total of 3 rolls; however, among the 3 you want to have at least one of the specific type you like the most (blueberry)
a) How many ways are there to choose?
b) If the baker randomly picks bagels for you, what is the probability that you will get what you like?
2. how many 2 letter words could you design using english alphabet having 26 letters? Two same letters, e.g. "OO", are not permited.